Human Fetal Period-A General Survey

8/9/2019 Human Fetal Period-A General Survey

1/42


2/42

PERIOD OF FETUS

The period from the beginning of the 9th

week to birth is known as fetal period.

In it differentiation continues and organs

become competent to assume their

specialized functions.


3/42

Transformation ofembryo to fetus is gradual.CRL or CHL

Growth in length is particularly striking during the3rd, 4th and 5th months

While increase in weight is most striking during thelast 2 months of gestation.


4/42

MONTHLY CHANGES

The growth of thehead during fetal period is slow

compared to the rest of body.

At the beginning of 3rd month, thehead constitutesapproximately of crown rump length (CRL).

By the beginning of 5th month, the size of thehead

is about 1/3rd of crown heel length (CHL)

At birthis approximately 1/4th of CHL.


5/42


6/42

THIRD MONTH (9-12 wks)

FACE: Morehuman looking broad faceHEAD:

Disproportionately large

Makes up nearly half of the fetus' sizeEYES:

Directed ventrally

Eyelids fus

ed

EARS:

Rise to their definitive position on the side ofhead


7/42

LIMBS: Reach their relative length

PRIMARY OSSIFICATION CENTERS:Arepresent in the long bones and skull by the 12th

week

.


8/42

PREUMBLICAL HERNIATION: During the 6th week,

intestinal loops cause a large swelling (physiological

herniation) in the umbilical cord.

By the 12th week, loops withdraw into the abdominal cavity.


9/42

11th week fetus: Intestines are no longer in the

umbilical cord


10/42

ERYTHROPOIESIS, : At 9th week liver is the major

site, after 12th week activity is reduced and begins in

spleen

EXTERNAL GENITALIA:Appear well differentiated

MUSCULAR ACTIVITY: Evoked in aborted fetuses


11/42


12/42

4TH AND 5TH MONTHS

During the

4th

and 5th

months, t

hefetus l

engt

hensrapidly and at theend of first half of intrauterine life, its

CRL is approximately 15cms, about the total lengthof newborn.

Weight is less than 500 gm


13/42

Fine downy hairs (LANUGO)Head and eye brow hairs

Fetal movements (QUICKENING)

Mother may feel a FLUTTERING in the lowerabdomen


14/42

17 week fetus: Thin skin with little S/C

tissue


15/42


16/42

6TH AND 7TH MONTHS

During the 2nd half of IUL, weight increasesconsiderably and particularly during last 2.5 months,when 50% of the full term weight (approx. 3200gms)is added.

During the

6th

month, the

skin of t

hefetus is r

eddis

hand has wrinkled appearance because of the lack of

underlying connective tissue.


17/42

The respiratory and the central nervous system havenot differentiated sufficiently, and coordinationbetween the two systems is not yet well developed.

By 6.5 to 7 months, fetus has length of about 25 cmand weighs approximately 1100gms.

If born at this time, the infant has a 90% chance ofsurviving.

Respiratory movements

Sucking movements

Some sounds can beheard


18/42


19/42


20/42


21/42

NINTH MONTH (33-36 wks)

SKIN:Dull redness of the skin fades

Wrinkles smooth out

Lanugo begins to disappear

BODY AND LIMBS:

Become rounded

Body fat increases


22/42

VERNIX CASEOSA: By theend of IUL, the skin iscovered by a whitish fatty substance


23/42

At theend of 9th month,the skull has the largest

circumference of all parts

of the body.

At the time of birth, theweight of a normal fetus

is 3000 to 3400gms, its

CRL is about 36cms,

and its CHL is about50cms.

Testes are in the

scrotum (end of 9th

month)


24/42


25/42

GROWTH IN LENGTH & WEIGHT

DURING FETAL PERIOD

Age (weeks) CRL (cm) Weight (g)

9 -12 5 - 8 10 - 45

13 - 16 9 - 14 60 - 200

17 - 20 15 - 19 250 - 450

21 - 24 20 - 23 500 - 820

25 - 28 24 - 27 900 - 1300

29 - 32 28 - 30 1400 - 2100

33 - 36 31 - 34 2200 - 2900

37-

38

35 -

36 3000-

3400


26/42

DEVELOPMENTAL HORIZONS

DURING FETAL LIFE

EVENTS AGE (weeks)

Taste buds appear 7

Swallowing 10

Respiratory movements 14 16

Sucking movements 24

Some sounds can be heard 24 26

Eyes sensitive to light 28


27/42

TIME OF BIRTH

The date of birth is most accurately indicated as 266days, or 38 weeks, after fertilization.

Theoocyt

eis usually f

ertiliz

ed wit

hin 12

hours ofovulation.

The sperm deposited in the reproductive tract up to6 days prior to ovulation can survive to fertilizeoocyte.

Thus most pregnancies occur when sexualintercourse occurs within a 6-day period that endson the day of ovulation.


28/42

The obstetrician calculates the date of birth as 280

days or 40 weeks from the first day of last menstrual

period.Most fetuses are born within 10 to 14 days of the

calculated delivery date.

If they are born muchearlier, they are called as

premature

If born later, they are called postmature.


29/42

MEASUREMENTS AND CHARACTERISTICS

OF FETUSES

Various measurements and external characteristics are

useful forestimating fetal age.

Until theend of first trimester, CRL is the method of choice

(1-2days). In the second and third trimesters, several structures can be

identified and measured ultrasonographically

Gestational sac appear on transabdominal sonography at 5th

week (embryo at7th

week) and approx a weekearlier by TVS(embryo at 6th week)


30/42

ULTRASONOGRAPHY MEASUREMENTS

BPD

Head circumference

Abdominal circumference

Femur length

Foot length

Fetal weight


31/42

CROWN RUMP LENGTH


32/42

BI-PARIETAL DIAMETER


33/42

CIRCUMFERENE


34/42


35/42

FEMUR LENGTH


36/42

FOOT LENGTH


37/42

FACTORS INFLUENCING FETAL GROWTH

Following factors stimulate fetal growth:

Glucose

Aminoacids

Insulin (secreted by fetal pancreas)

Insulin like growth factors

Human growth hormone


38/42

IUGR

Term applied to infants who are at or below the 10th percentile for their

expected birth weight at a given gestational age.

Small for dates or small for gestational age

Incidence is 1 in 10 babies


39/42

FACTORS CAUSING IUGR

Cigarette smoking

Alcohol consumption

Maternal malnutrition

Faulty food habitsMultiple pregnancies

Drug addiction

Impaired uteroplacental and fetoplacental blood flow (

small chorionic v

essels, s

everehypot

ension,placental dysfunction or defect and renal diseases)

Genetic factors and growth retardation (recessivegenes, structural and numerical chromosomalaberrations)


40/42

Q. The fatal period extends from the

4th to 8th week

9th week to term

12th week to term

6th week to term


41/42

Q. With respect to fetal growth

an increase in length is most striking during early portions of the fetal

period, while increases in weight are most significant during the last 2

months of gestation an increase in weight observed early in gestation, whereas striking

increases in length occur later

both fetal length and weight increase at a steady rate throughout gestation

there is an initial lag phase afterembryogenesis followed by a striking

increase in both length and weight during the last 2 month of gestation


42/42

Documents

Human Fetal Period-A General Survey